*3.2.10. Vitamin and mineral supplementation*

Vitamin and mineral supplements help to develop immune response by acting on the immune cell or by changing metabolic or endocrine functions [47]; as a result, the antibodies are produced in the body at a faster rate and a protective level of antibodies is gained in a shorter time. Vitamin E and selenium have a role in modulating the immune response and have shown good results in preventing vaccine failure. Research conducted shows that vitamin E may enhance immune response to antigens in cockerels but excessive vitamin E may depress specific immune responses [48]. Administration of excess vitamins, amino acids, minerals and their combinations enhance the disease resistance by stimulating humoral and cellular immunity and phagocytosis [49]. Optimal vitamin nutrition is required for optimal immune response and disease resistance. The addition of higher levels of vitamin A, C, E and Selenium ensures better immune response of birds to vaccination and reduces the chances of vaccination failure in broiler poultry flocks [50]. Studies have suggested that the nutrient levels that are adequate for growth and feed efficiency may not be adequate for normal immunity for maximizing the resistance to disease [51, 52].
